A pediatric transitional ankle fracture that classically appears as a Salter-Harris type III fracture on an anteroposterior (AP) radiograph and a Salter-Harris type II fracture on a lateral radiograph is known as a:
A
Tillaux fracture
B
Snowboarder's fracture
C
Pilon fracture
D
Triplane fracture
Explanation
The triplane fracture is a complex transitional fracture of the distal tibia that crosses three planes, radiographically appearing as a SH III on AP and SH II on lateral views.
Clinical Context: Transitional ankle fractures occur during adolescence (typically ages 12-15) when the distal tibial physis is actively closing. Physeal closure occurs in a predictable asymmetric pattern: central -> anteromedial -> posteromedial -> lateral. The anterolateral physis remains open the longest, making it vulnerable to external rotation forces.
- Triplane Fracture: Involves the sagittal, coronal, and transverse planes. The classic 2-part triplane fracture consists of an anterolateral epiphyseal fragment attached to a large posterior metaphyseal spike. Because it crosses planes, it projects as a SH III (epiphyseal vertical line) on the AP view and a SH II (metaphyseal spike) on the lateral view. CT is mandatory to assess articular step-off. Intra-articular displacement > 2 mm requires operative reduction (CRIF or ORIF).
- Tillaux Fracture: An avulsion of the anterolateral epiphysis by the anterior inferior tibiofibular ligament (AITFL). It is a pure SH III fracture, visible only on the AP/Mortise view.
References:
1. Cooperman DR, et al. 'A three-dimensional study of the normal development of the distal coronal tibial physis.' J Pediatr Orthop. 2001.
2. Ertl JP, et al. 'Triplane fractures of the distal tibia.' J Pediatr Orthop. 1988.